To preserve or not to preserve thread color

[plecopterahopper]

I built a rod and added a decorateve but wrap using both NCP thread and silver. The shop helping me with the finish doesn't use color preserver on their rods, but they also don't do decorative stuff either. I want to use color preserver so that the silver doesn't show through the top thread on the wrap. The guys at the shop said that color preserver is very difficult to use because it leaves blotchiness. Is there a way to avoid blotchiness with color preserver? What tricks should I know? Thanks advanced,
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